Whether a home is newly purchased or long inhabited, an updated kitchen, a new deck or even a coat of fresh paint can make it feel spiffier. When it comes to luxury real estate, however, some homeowners take upgrades to an extreme, spending big bucks on outrageous amenities.

We pulled together a list of upscale abodes for sale or just sold that have been equipped with fantastic, unusual — and in some cases downright wacky — amenities. These are not your typical luxe enhancements like home theaters, wine cellars and game rooms, although most of our estates have those features too. Our friends at Trulia.com, Realtor.com, Sotheby's International Realty and Coldwell Banker Previews International helped us uncover these unique listings.

The $10 million cliffside dwelling at Point Place in Laguna Beach, Calif., would make Bruce Wayne proud. The driveway has a secret, subterranean entrance below the house's steep perch, inside the cliff itself. Once a car passes through the hidden garage door, a commercial-grade hydraulic lift transports it up and into the house.

Even among snazzy home swimming holes, Las Vegas' $10 million Wood Creek Court residence stands out. It has a full-on water park with sandy beach island, a sunken swim-up bar--even a lazy river. The owners of the $7.4 million French Bastide in Greenwich, Conn., converted an English phone booth into a poolside outdoor shower. Recently Sotheby's International Realty sold a Beverly Hills home, complete with a giant bird-shaped swimming pool, for $4.2 million. As if a winged body of water wasn't enough of a talking point at house parties, the owners also dug out an underwater observation room.

Other homes have indoor water works. The $3.4 million Midwest Club estate in Oak Brook, Ill., is on the market for $3.4 million, thanks in part to waterfront views and seven bedroom suites with private living areas and a foliage-lined indoor koi stream. The koi stream warps around a little island holding a ficus tree, while the stream's banks nourish dozens of plants. If you want to access the far side of the room, a stone-tiled bridge will take you there.

"I have a lot of fun showing it," gushes Carol Lee Cikanek, the property's listing agent at Coldwell Banker Previews International. "I think the buyer of this home is certainly not going to be someone who says, 'this is exactly what I've been looking for.' It's going to be the opposite. The buyer says 'I never thought I would buy a home anything like this, but it's just way too cool to pass up!'"

High-end homes with outrageous and wacky amenities lure many a gawker, but attracting real buyers can be tricky. Luxury homes with unusual amenities speak to a small niche and can sit on the market for longer periods of time, waiting for the right buyer to come along.

"The quirkier they (extreme amenities) are, the more they complicate the prospects of reselling the property," says Tara-Nicholle Nelson, consumer educator at Trulia.com, a San Francisco real estate listing site. However, she also notes, "Some of the extreme high-end home features actually create a clear way for sellers to differentiate their otherwise already highly attractive home from the other uber-opulent homes on the market."

Hall Willkie is president of Brown Harris Stevens, a New York real estate firm that represents a $35 million Manhattan townhouse boasting a two-story indoor wall of water. Willkie says both the pool of potential buyers and the selection of homes with opulent amenities are small.